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Best Steel (and Angle) for Cardboard Cutting

Discussion in 'General Knife Discussion' started by Sharperthansticks, Dec 18, 2019.

  1. DeadboxHero

    DeadboxHero Triple B Handmade, Custom Knives Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    No, it's not that you're not cooking the edge more with a Polished edge cutting cardboard. The toothy edge is just exposing more carbides at apex and has more surface area to wear down.

    You also need to rule out the variables.

    Perhaps the Polished edge being made is not optimal due to being crushed at the apex, rounded over while trying to create it.

    Simple things have to be ruled out before making complex conclusions.

    Eli Chaps and 115Italian like this.
  2. abcdef


    Oct 28, 2005
    Lots of information above. I would have never guessed that the most super of steels was the answer to cardboard.

    I just stomp it.
    chiral.grolim and Mecha like this.
  3. farid.


    Oct 26, 2010
    My experience in the last few months has been M35 HSS cuts incredible, I will try and upload some pics of a test I can do in the next couple of weeks.
    Farid Mehr
    jpm2 likes this.
  4. eveled

    eveled Gold Member Gold Member

    Mar 11, 2016
    Cardboard is tough on blades. I use a utility knife mostly at work for cardboard but at home I use an Russel Dexter rope knife. Goes through multiple layers like butter never needs sharpening. Best $4 I’ve ever spent.
    6F0FF638-1ECD-4C9B-8DA4-853F069EBC3F.jpeg B780F638-8A79-4DC4-84F4-12A60CC170B7.jpg
    CanadaKnifeGuy likes this.
  5. Mecha

    Mecha Titanium Bladesmith Knifemaker / Craftsman / Service Provider

    Dec 27, 2013
    eveled your sig line says, "I'm not afraid of cutting on a pate." Is that meant to say "plate? because a pate is the top of a head, which is cool too.
  6. jpm2


    Nov 19, 2014
    Yes, it does. I have a few made from parting tools that are among my best blades.
  7. eveled

    eveled Gold Member Gold Member

    Mar 11, 2016
    lol. Should day plate. It was from a thread a while back about using your pocket knife to cut a steak. Seems there are two type of knife owners. Those who are terrified of cutting on ceramic plates, and daredevils like myself who are willing to risk it all.

    funny that I don’t see my own signature line on posts.
    Last edited: Dec 19, 2019
    Mecha likes this.
  8. Chronovore

    Chronovore Basic Member Basic Member

    Aug 29, 2019
    Cardboard seems to be the material of choice for cut testing among YouTube reviewers. I've seen some talk about it being standard enough for relative repeatability. My experience with Amazon boxes has been fairly benign. Other cardboards, I'm not so sure.

    I recently picked up a box of Hammermill copy paper. I stacked the reams on my shelf and cut up the box. The cardboard was a little tougher than usual. When I finished, I noticed several tiny scratches on the sides of my 14C28N blade. The lighter color box might have been hiding some dirt. I'm guessing there was grit inside the cardboard.
  9. Mecha

    Mecha Titanium Bladesmith Knifemaker / Craftsman / Service Provider

    Dec 27, 2013
    Aha, it says "plate" now, which makes more sense but is not as funny as the image of cutting on a pate. :D The question is, what's the best knife for cutting on a pate? Sounds like a question for Prac Tac.
    eveled likes this.
  10. tomhosang


    Feb 17, 2017
    I'd pay close attention to what @DeadboxHero said. There's no way that any steel (even 8Cr), should be dull after just one box. The steels you mentioned (M390, S90V, S110V, etc.) should be enough to get you through weeks of use without needing much of a touch up. It almost sounds like there's some remnants of a burr there. Your last few strokes on the KME should be very light and continuously moving along the edge. Also keep in mind that every time you strop (especially with that green compound), you're just realigning the edge and not sharpening really. There is still fatigued steel there unless you give it a full resharpening to get rid of it.
    DeadboxHero likes this.

    USMCPOP Gold Member Gold Member

    Jan 6, 2016
    Keep your eyes open. I've gotten two 100-packs of made-in-USA blades for $10.
    chiral.grolim likes this.
  12. CanadaKnifeGuy


    Jan 27, 2019
    Gerber EAB and a pack of spare blades. No brainer.
  13. chiral.grolim

    chiral.grolim Universal Kydex Sheath Extension Knifemaker / Craftsman / Service Provider

    Dec 2, 2008
    I have yet to see good data on heat from hand-use of a knife corrupting the edge, but it something that has been brought up in discussions of using coolant while sharpening. Cutting up cardboard, like chopping hard wood, generates a LOT of frictional heat, but that is mostly behind the apex where the bevels slide through and is minimized by using a thinner blade (less wedging).

    You are absolutely right that a toothy edge, even a serrated edge, has less surface area contact upon initial penetration (= sharper than a blade with more contact area at penetration), but once the entire edge enters the medium, all of it is making contact and now you have the benefit of a longer edge cutting through at different angles due to the scalloping of the serrations (like cutting a piece of paper or a reed-stalk perpendicular vs at an angle, using the material's own stiffness to your advantage). Toothy edges are awesome for any cutting that doesn't demand a smooth surface left behind (e.g. shaving, planing wood, cutting microscopy specimens, making surgical cuts to be sutured later) :thumbsup::thumbsup:

    Image of a DMT 1200 finish from ToddS' blog: https://scienceofsharp.com/2014/04/13/the-bevel-set/


    Maxamet finished up with abrasives too soft to shape the carbide but sufficient to expose them by reducing the surrounding matrix, users indicate prolonged slicing aggression :cool::


    The bolded above is false, as demonstrated by TEM

    Realignment happens with any sharpening, it simply depends on the amount of mis-alignment and the method undertaken to correct it. Any process by with the diameter of the apex is reduced is "sharpening", and stropping with compound on an edge that can be affected by it definitely does this, producing a keener microconvex edge. Stropping without compound can act as "burr removal" by breaking away the apex material and leaving behind a LESS refined edge that then requires resharpening with abrasive. Using any kind of metal or ceramic rod will also remove material via adhesive wear (galling) which can either ruin or improve the edge depending on the situation (e.g. at too close of an angle, the adherence can rip away a well-formed apex vs at a higher angle it can create a new microbevel with a keener apex). The rod can also realign your edge.

    One more piece from ToddS' blog:
    ZDP189 stropped for a keen edge that excels at push-cutting (shaving, paper) but fails the "three finger slide test" of sharpness (i.e. no 'bite'), apex ~0.2um:

    ZDP189 NOT stropped but finished on DMT1200 that has aggressive bite and slicing but won't push-cut paper cleanly, apex >1um (5x thicker):

  14. chiral.grolim

    chiral.grolim Universal Kydex Sheath Extension Knifemaker / Craftsman / Service Provider

    Dec 2, 2008
    The bolded above is incorrect in the context presented.
    While you could consider the hills and valleys as "more surface area" on the toothy edge, a direct comparison to the same amount of surface area on less toothy edge (i.e. using more edge length for cutting) will still result in using more force to cut with the less aggressive less toothy edge because the more toothy edge leads with those teeth which act as penetration points throughout the cut, and the sides of those points act on the medium at different angles allowing for more aggressive cutting as well. The same principles apply in saw blades. Normalizing for edge-length (or surface area) doesn't change the geometry doing the cutting. Like you typed, "simple things".
  15. tomhosang


    Feb 17, 2017

    Okay, so I read through that entire article (love that site btw). I did not see anything that either supports or refutes either argument about stropping. The way I think of it is this: After a fresh sharpening, the edge is at its maximum potential. The cutting edge is going to last the longest from this point. Through use, the apex is going to become fatigued and become "dull." Now you can strop it and bring it back to a reasonable level of sharpness, but it will not cut as long as it did after the initial sharpening because there is still more fatigued steel there than can be removed by stropping. In theory, the edge retention will become less and less with each subsequent stropping. This has been somewhat proven by a friend of mine who does some cut testing.

    In regards to Maxamet, you most definitely can get a good edge with abrasives that aren't hard enough to abrade the carbides. This does effect the longevity of the edge however. I did some long term testing on Maxamet a few months back and ran into some issues when using something other than diamond to sharpen. Before performing a cut test, I put Maxamet through my normal progression of 200-1000 diamond and then finished it on 1200/1600 grit ceramics. My results were good but not quite to the level I expected from Maxamet. After a conversation with @DeadboxHero, I ran the test again after using a strictly diamond progression (200 to 1000) and it resulted in a 24.38% increase in edge retention. I think abrasives matter a ton in the performance of these super hard, exotic steels since the matrix is much harder than normal (measured at 69.2 HRC for this particular knife), and key to holding those ever important carbides in place for maximum performance. This is obviously all based on my experience, so take this for what it's worth.

    TL;DR: You can get any steel sharp with most abrasives. To get the maximum performance, however, you need to use the correct abrasives.
    DeadboxHero likes this.
  16. FortyTwoBlades

    FortyTwoBlades Baryonyx walkeri Dealer / Materials Provider

    Mar 8, 2008
    Basically any high-vanadium steels are going to need diamond or CBN for proper performance once you step above ANSI 400 grit.
  17. DeadboxHero

    DeadboxHero Triple B Handmade, Custom Knives Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    Well, we are trying to keep things simple, it is implied here that we are using the same Geometry and making a nice apex but roughing up the finish and exposing more carbide.

    I see you have interpreted this as literally the surface area of the bevel in itself.

    chiral.grolim likes this.
  18. DeadboxHero

    DeadboxHero Triple B Handmade, Custom Knives Knifemaker / Craftsman / Service Provider

    Mar 22, 2014
    Isn't that facinating? It looks like Todd Simpson's SEM work shows that the mechanism is the breaking of the carbides to shape. They aren't being pulled out if the matrix is at high hardness.
    So if sharp is simply a shape than it's being achieved but with lots of fatigue and a busted up edge.
    With Diamond/CBN we can shape all the Carbides into the apex without fatigue.

    This is facinating because we have seen some groups in the knife community refuse to accept that diamond/CBN is what should be used for these types of steels yet they will often complain about lower performance and not connect the dots.

    I've seen some feel there is a grand conspiracy of diamond/CBN stones justifying their existence to make lots of money.

    There is no money in making these exotic stones as much as there is in making pull through sharpers with gimmicks so it's a laughable argument.

    The truth is it's just a complex subject and easy for folks to get glazed over when discussing the details.

    Really it takes guys like you Tom that do testing and can share Differences between things.

    At the end of the day though folks will have to test it themselves and right or wrong whatever they like and use is king for them.

  19. chiral.grolim

    chiral.grolim Universal Kydex Sheath Extension Knifemaker / Craftsman / Service Provider

    Dec 2, 2008

    This was the part about stropping BARE removing material and is coupled to images of it (6th and 7th images):
    The entire next section details abrasion from stropping without compound. For stropping WITH compound (as was the original context), those images+descriptions are found in the "Pasted Strop" section starting here: https://scienceofsharp.com/2015/02/09/the-pasted-strop-part-1/

    In regard to "after a fresh sharpening", stropping with abrasive IS "sharpening". Using proper technique, it produces a microconvex edge with the lowest stable (i.e. most durable) apex diameter you are likely to achieve prior to cutting. However, once this edge is worn down to the sufficiently thicker apex diameter to become a nuisance, it's likely that a LOT (relatively speaking) of material needs to be removed from the bevels to return to the geometry you desire, and stropping at high grit to get there may simply take too long so we move to a lower grit hone (preferably hard and flat) and cut a larger bevel (at low angle) before doing the finishing strop = "resetting the bevel". :thumbsup: I think that is what you are typing about. Yeah, stropping back the edge over and over again is just increasing the bevel angle in the microconvexity, leaving an edge that while equally thin is apex diameter is slowly becoming less and less acute = requires more force to cut = wears more on the edge = worse and worse edge retention. :thumbsup:

    For the maxamet, yup, abrasives are key, although i doubt that the matrix is really any harder, rather the carbide content is so much higher in distribution that the Rockwell test picks up more of this in its measurement = harder steel despite same martensite matrix hardness. Someone can correct me on that. It's similar for cemented carbide (like the Sandrin blade) - the tungsten carbide is very very hard while the cobalt matrix is not, but a high ratio of carbide:matrix produces higher RC and, oddly enough, higher toughness. However, cemented carbide is 70-95% carbide vs cobalt binder/matrix and behaves differently than steel (much lower toughness, much higher hardness and wear resistance), Maxamet is only ~17% carbide, but one property that is key is that increased cobalt slows the coarsening of carbides, keeping them fine and well distributed which, as mentioned, factors into what the rockwell test is measuring - having a lot of tiny well distributed carbides throughout the matrix will lead to a high reading.
    So consider that - the microhardness of the matrix in maxamet isn't all that different, it isn't really any "better" at holding onto carbides, it simply has more carbides in it. Carbides don't usually "fall out" of an edge (at least I haven't seen support for that beyond arm-chair theorizing), but they can be cracked/chipped and they can be cracked out if precipitated at grain boundaries.

    I will note that this is NOT based on my own experience, this is from reading articles by people running experiments and publishing data and images to support their conclusions. I am happy to be corrected by others with supporting data (and can provide some of my own), but I am simply discussing the mechanisms as they are understood. Far more important than the precise mechanism is the experience, imho. If a technique works well for you, knowing the "why" is only important so far as needing to explain it and improve it, but knowing that it works is sufficient for the task at hand ;) But we still want to know why.
    David Richardson and tomhosang like this.
  20. chiral.grolim

    chiral.grolim Universal Kydex Sheath Extension Knifemaker / Craftsman / Service Provider

    Dec 2, 2008
    Yes, I thought that was what you meant by "more surface area to wear down" - the area of the edge length x width. I don't think most people think about the width of the apex really, even though that is what gives a blade its sharp edge.

    I'd like to see some "after" SEMs comparing a coarse edge to a plain edge prepared like you typed and then put through a wear test until the first blade gets too dull to go on - what is the wear profile of each, how thick is the apex of the plain edge and the condition of the "teeth" of the coarse edge? Those images must exist somewhere...

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